1. Field of the Invention
This invention relates to an improved seat suspension arrangement, more especially of the kind intended for use in the backrest of a vehicle seat.
2. Related Art
In the vehicle seat, it is well known to provide support for the upholstery of the seat by means of a platform element that is suspended between two opposite side elements of a seat frame in such a manner as to provide resilient support for the upholstery. Arrangements are known in which the platform element is flexible but substantially inextensible, and wherein tension springs are provided to support the platform element between the side elements of the seat frame. Other arrangements are known wherein the platform element itself is resiliently extensible in a transverse direction, and in that case the platform element can be attached to side elements of the seat frame by link means that are substantially inextensible. Platform elements of the latter kind are known, for example, from EP-A-0128407 (see FIG. 2) and GB-A-2316604 (see FIG. 1).
Safety requirements in relation to vehicle seats become increasingly more rigorous, and thus, in the design of vehicle seats, those skilled in the art are constantly seeking measures that may be adopted in order to reduce personal injury that may occur to occupants of the seats in the event of a motor vehicle accident.
It has, for example, been proposed that the frames of vehicle seats should be adapted to allow a limited collapse in the event of the application of sudden loads exceeding those occurring in normal use, in order, for example, to reduce injury to an occupant due to sudden forward acceleration of the seat. This may occur, for example, if a motor vehicle is subjected to a sudden impact from the rear when a following vehicle collides therewith.
Arrangements for providing for the collapse of vehicle seat frames, are, however, of complicated construction and are thus relatively expensive.
Other arrangements for collapse of seat suspension assemblies have also been proposed but are also relatively complicated, see for example WO 99/29536